Effect of crystalline versus protein-bound lysine on plasma amino acids in exercising horses

Abstract

Donkey farming is expanding because of the rediscovery of nutritional properties of jennies’ milk for human consumption. In livestock, timed artificial insemination (TAI) allows to manage big herds without estrus detection, but there are very few studies on estrus synchronization in jennies. The aims of this study were to compare three different combinations of prostaglandin F2α (PGF2α) and gonadotropin-releasing hormone (GnRH) analogs for TAI in jennies and to compare the estrus or diestrus status diagnosed by ultrasonography with serum progesterone concentration. Nine fertile jennies were submitted to three TAI protocols: PPG (PGF2α, PGF2α, and GnRH), PGPG (PGF2α, GnRH, PGF2α, and GnRH) and GPG (GnRH, PGF2α, and GnRH). Ovarian activity was monitored until ovulation, and blood samples were taken for progesterone determination. Artificial insemination was done with a fresh-diluted semen. The comparison of the three TAI protocols showed a trend for difference in pregnancy rates per synchronized jennies (from 11% with PPG up to 56% with PGPG) although not statistically significant. Follicle diameter or the presence or absence of a corpus luteum at the beginning of the treatment did not affect synchronization response or pregnancy rate. Dominant follicle diameter, at the time of the last GnRH treatment, significantly affected the ovulation response. Ultrasound was confirmed to be highly accurate for the determination of the estrus or diestrus status. This study demonstrated the possibility to achieve reasonable synchronization and pregnancy rates in jennies using TAI protocols adapted from other species.